ramezan ali mahdavinejad

Ultrasonic vibration assisted single point incremental forming (UVaSPIF) is based on localized plastic deformation in a sheet metal blank. It consists to deform gradually and locally the sheet metal using vibrating hemispherical-head tool controlled by a CNC milling machine. The ultrasonic excitation of forming tool reduces the vertical component of forming force. In addition, application of ultrasonic vibration reduces the surface roughness of the specimen. Surface roughness is one of the quantitative and qualitative parameters, which is used to assess the quality of the final product. In the present paper, a statistical analysis and optimization of effective factors on this parameter is performed in the UVaSPIF. For this purpose, response surface methodology (RSM) is selected as the experiment design technique. The controllable factors such as vertical step size, sheet thickness, tool diameter, wall inclination angle, and feed rate is specified as input variables of the process. The obtained results from analysis of variance (ANOVA) and regression analysis of experimental data confirm the accuracy of mathematical model. Furthermore, it is shown that the linear, quadratic, and interactional terms of the variables are effective on the surface roughness parameter. To optimize the surface roughness parameter, the finest conditions of the experiment are determined using desirability method, and statistical optimization is subsequently verified by conducting the confirmation test.

Ultrasonic Vibration assisted Single Point Incremental Forming (UVaSPIF) process is an attractive and adaptive method in which a sheet metal is gradually and locally formed by a vibrating hemispherical-head tool. The ultrasonic excitation of forming tool reduces the average of vertical component of forming force and spring-back rate of the formed sample. The spring-back phenomenon is one of the most important geometrical errors in SPIF process, which appear in the formed sample after the process execution. In the present article, a statistical analysis and optimization of effective factors on this phenomenon is performed in the UVaSPIF process based on DOE (Design of Experiments) principles. For this purpose, RSM (Response Surface Methodology) is selected as the experiment design technique. The controllable factors such as vertical step size, sheet thickness, tool diameter, wall inclination angle, and feed rate is specified as input variables of the process. The obtained results from ANOVA (Analysis of Variance) and regression analysis of experimental data, confirm the accuracy of mathematical model. Furthermore, it is shown that the linear, quadratic, and interactional terms of the variables are effective on the spring-back phenomenon. To optimize the spring-back phenomenon, the finest conditions of the experiment are determined using desirability method, and statistical optimization is subsequently verified by conducting the confirmation test.

In this research, the machinability of iron-recycled grey cast iron powder metallurgy parts is investigated. For this purpose, grey cast iron swarfs were transformed to powders by target jet milling method and were then used to prepare powder metallurgy parts in combination with commercial iron powder. Green compacts were prepared with the variables of cast iron powder percentage and compaction pressure. Design of experiments was conducted by response surface method for sintered parts with the variables of cast iron powder percentage, compaction pressure, sintering temperature and sintering time each in five levels. Regression analysis and analysis of variance were used to investigate the effect of input parameters, develop the mathematical models and evaluate the validity of the models. In the green section, machinability was qualitatively investigated in drilling. For sintered parts, machinability was evaluated by measuring the thrust and torque forces and the obtained surface finish in drilling. The obtained results certificated the accuracy of the extracted regression equations for predicting the machining properties of the parts. Also, the results demonstrated that the addition of jet milled grey cast iron improves the machinability of iron-based powder metallurgy parts.

Incremental Sheet Metal Forming (ISMF) is based on localized plastic deformation. In this process, a hemispherical-head tool, controlled by a CNC milling machine, shapes a sheet metal according to a defined path. Study of the forming force is one of the most important topics in this process. Increasing of vertical step size, tool diameter, wall angle and sheet thickness together with using of high strength sheet metals and lightweight alloys, leads to an increase in the forming force. In this paper, the performance of a novel forming process, named Ultrasonic Vibration assisted Incremental Sheet Metal Forming (UVaISMF) has been investigated. The procedure of design, manufacture and test of vibratory forming tool, is presented. The occurrence of longitudinal mode and resonance phenomenon has been confirmed by the results of modal analysis and experimental test. Furthermore, the effect of ultrasonic vibration on the vertical component of forming force and spring-back has been studied. Aluminium sheet of grade Al 1050-O is used as a work material. Experimental results obtained from straight groove test, indicate that ultrasonic excitation of forming tool, will reduce the average of vertical component of forming force and spring-back in comparison to conventional process.

This study focused on the optimization of Al—Mg to CuZn34 friction stir lap welding (FSLW) process for optimal combination of rotational and traverse speeds in order to yield favorable fracture load using Grey relational analysis (GRA). First, the degree of freedom was calculated for the system. Then, the experiments based on the target values and number of considered levels, corresponding orthogonal array, Grey relational coefficient and Grey relational grade were performed. In the next step, Grey relational graph of each level was sketched. The performed graph and analysis of Grey results proved the impact of rotational speed and traverse speed on fracture load of resultant joints. Finally, the optimum amount of each parameter for better strength of the welds was obtained. This study showed feasibility of the application of Grey relational analysis for achieving dissimilar friction stir lap welds with the highest quality.

In this research، grey cast iron scraps were recycled into powders and were then used in combination with iron powder for producing iron based powder metallurgy parts. Design of experiments was conducted by response surface method for both the green and sintered parts. For the green properties، the parameters cast iron powder percentage and compaction pressure، and for the sintered parts، the mentioned parameters in addition to sintering temperature and sintering time were selected each in five levels as the input process parameters. Transverse rupture strength and elastic modulus were measured as the responses. Regression analysis and analysis of variance were used to investigate the effect of input parameters، develop the mathematical models and evaluate the validity of the models. Scanning electron microscopy and optical microscopy micrographs were provided to better understanding. The obtained results، in addition to determine the effects of the input parameters، demonstrated the adequate mechanical properties of the produced parts in industrial scales and the validity of the proposed models. Also، the proposed method demonstrated its good capability for estimation of elastic modulus of powder metallurgy parts.